Page:The Zoologist, 4th series, vol 2 (1898).djvu/327

Rh collateral affinity with the Trypanidæ, traceable to their common descent. The rather confusing cross-relationships between these several families are characteristic of little-specialized forms; it is as if one had to disentangle a network of small divaricating twigs close to the stem, whilst the course of the larger branches is comparatively easy to trace.

The Pyralidina are commonly distinguishable from the other groups already mentioned by the structure of vein 8 of the hind wings, which is brought down so as to closely approach or anastomose with vein 7 beyond the cell. Another character almost constant throughout the group is the stalking of veins 8 and 9 of the fore wings; it is quite constant in most of the families, but in the mainly tropical family Thyrididæ these veins are more usually separate; we may therefore with considerable probability regard the Thyrididæ as ancestral. Finding further that they nearly approach the Heterogeneidæ, both structurally and superficially, whilst the other families are of a peculiar type which is remote from anything else, we shall be justified in looking to the Heterogeneidæ as the origin of the group. The mutual relations of the nine families composing this extensive division need not be discussed here in the main; but the case of the Pterophoridæ may be mentioned. These curious insects, the well-known "plume-moths," usually have the wings very narrow, and split into two or three feather-like lobes; hence the neuration tends to be much degraded for want of room, but in the earliest forms (and recognizing the transition afforded by the small Australian family Tineodidæ) it approaches the Pyralid type; with which also the unusually long and slender legs, the structure of the head, and the larval appearance and habits are also in accordance. The Orneodidæ (in which each wing is split into six plumes) can be traced to the same source.

Coming now to the groups which have vein 1 c of the hind wings constantly absent, it will be convenient to study first the Papilionina, generally termed "butterflies." Notwithstanding the amount of attention bestowed on this attractive group, little has been written as to its origin. It is characterized by the clubbed antennae, and absence of the frenulum, both these features being found in other cases but not in combination. As it falls into two sections, of which one (Hesperiadæ) has all the veins of